Scheduler optimization for OFDMA downlink transmissions

ABSTRACT

Systems and methods are provided for optimizing the scheduling of Orthogonal Frequency-Division Multiple Access (OFDMA) transmissions in the downlink (DL) direction. A two-stage mechanism can be implemented when effectuating DL OFDMA transmission involving multiple modulation and coding schemes (MCS) in a single transmit burst. A first stage of the two-stage mechanism may use radio frequency (RF) boosting/de-boosting of Resource Units (RUs) such that the average input power to an AP power amplifier (PA) may remain under a saturated PA output power to ensure PA linearity. If RF boosting/de-boosting is not supported, an alternative mechanism for OFDMA grouping (to rigid grouping) can be employed to skip higher MCS.

DESCRIPTION OF THE RELATED ART

Wireless digital networks are becoming ubiquitous in enterprises,providing secure and cost-effective access to resources. Those networksusually have one or more controllers, each controller supporting aplurality of access points (AP) deployed through the enterprise. WiFinetworks operating in accordance with IEEE 802.11 standards are examplesof such networks. Wireless network communications devices (also referredto as stations or client devices), such as personal computers and mobilephones transmit data across wireless digital networks vis-à-vis WiFiAPs, and cellular network APs, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure, in accordance with one or more variousembodiments, is described in detail with reference to the followingfigures. The drawings are provided for purposes of illustration only,and merely depict typical or example embodiments. These drawings areprovided to facilitate the reader's understanding of various embodimentsand shall not be considered limiting of the breadth, scope, orapplicability of the present disclosure. It should be noted that forclarity and ease of illustration these drawings are not necessarily madeto scale.

FIG. 1 is a schematic block diagram illustrating an example networkconfiguration in which the technology described herein may beimplemented.

FIG. 2 illustrates example circuitry of an example access point in whichthe technology described herein may be implemented.

FIG. 3 illustrates examples of resource unit boosting/de-boosting inaccordance with various embodiments.

FIG. 4 illustrates an example effective isotropic radiated powerhistogram in accordance with various embodiments.

FIG. 5 illustrates an example of conventional rigid orthogonal frequencydivision multiple access grouping.

FIG. 6A illustrates a first aspect of transmission scheduling inaccordance with various embodiments.

FIG. 6B illustrates a second aspect of transmission scheduling involvingenhanced orthogonal frequency division multiple access grouping inaccordance with various embodiments.

FIG. 7 is a block diagram of an example computing component or devicefor optimizing scheduling of orthogonal frequency division multipleaccess downlink transmissions in accordance with one embodiment.

FIG. 8 is an example of a computing component that can be used inconjunction with various embodiments of the present disclosure.

The figures are not intended to be exhaustive or to limit variousembodiments to the precise form disclosed. It should be understood thatvarious embodiments can be practiced with modification and alteration.

DETAILED DESCRIPTION

Various embodiments disclosed in the present application are directed toa computer-implemented system and method of optimizing the scheduling ofOrthogonal Frequency-Division Multiple Access (OFDMA) transmissions inthe downlink (DL) direction (from an AP to a client device). A two-stagemechanism can be implemented when effectuating DL OFDMA transmissioninvolving multiple modulation and coding schemes (MCS) in a singletransmit burst. A first stage of the two-stage mechanism may use radiofrequency (RF) boosting/de-boosting of Resource Units (RUs) such thatthe average input power to an AP power amplifier (PA) may remain under asaturated PA output power to ensure PA linearity. If RFboosting/de-boosting is not supported, an alternative mechanism forOFDMA grouping (to rigid grouping) can be employed to skip higher MCS.

To provide background/context, the aforementioned feature known as OFDMAis an “access” technique, an refers to a version of OrthogonalFrequency-Division Multiplexing (OFDM) that was introduced in theInstitute of Electrical and Electronics Engineers (IEEE) 802.11ax. OFDMAallows for dedicating different sub-carriers to different clients withinone transmission burst. In particular, OFDMA enables concurrent APcommunication in both the DL and uplink (UL) directions with multipleclient devices by assigning subsets of subcarriers, referred to as RUsto those individual client devices. The 802.11ax standard utilizes OFDMAtechnology for efficient access. This is in contrast to OFDM technologywhich does not allow for different modulations/transmit powers to beused on different data subcarriers within one transmission burst. Allsubcarriers within one data symbol and hence all data symbols within onetransmit burst would have the exact same modulation and transmit (TX)power would be equally divided among all data subcarriers. Of course,the two WiFi bands (2.4 GHz and 5 GHz) would need to comply with bandspecific PSD (Power Spectral Density) requirements to remainFCC-compliant.

An OFDM symbol may be thought of as a basic building block of a WiFitransmission. That is, an OFDM symbol is a small segment in time ofmodulated subcarriers, carrying information. In 802.11ax, subcarrierspacing was changed to allow for OFDMA to extend to small sub-channels(defined in the standard), each sub-channel having at least one (butusually two) pilot subcarriers. With a 2 MHz minimum sub-channel size, asmaller subcarrier spacing loses a smaller percentage of the overallbandwidth to pilots. Moreover, the number of guard and null subcarriersacross a channel can also be reduced as a percentage of the number ofuseable subcarriers, which in turn results in an increase in theeffective data rate of a given channel.

OFDMA works by dividing a transmission across the frequency dimension,with pairs of devices assigned to transmit and receive in sub-channelsor RUs of a main RF channel. This allows an AP (in the downlink) tobundle multiple frames together in different sub-channels in a singletransmit burst opportunity, while the AP's associated client devicestune their respective radios to different sub-channels to receive theirrespective transmissions. In particular, an AP may assemble a number offrames for different client devices, and modulates them over a set ofallocated sub-channels. Padding can be added to a frame when the frameis shorter than a longest frame of a bundle.

RUs can contain a significantly less number of sub-carriers dedicated toone client device. For example, in accordance with the 802.11acstandard, all 52 data subcarriers in a 20 MHz channel bandwidth would beallocated to one client per transmit burst. In contrast, and in an802.11ax 20 MHz channel bandwidth, nine 2 MHz RUs can be allocated tonine different client devices, where theoretically, all of the clientdevices can have different modulations and transmit powers within onetransmit burst. The minimum number of subcarriers per client device canbe 26, which forms an approximately 2 MHz RU. The number of subcarrierswithin a dedicated RU to a user can range from 26 to 996 depending uponclient requirements and channel bandwidth being used.

A purported fundamental advantage to using OFDMA is the reduction inlatency for all client devices in general. For example, with 802.11acOFDM transmissions, one transmit burst can cater either to highermodulation client devices with a high Signal-to-Noise ratio (SNR) thatare located closer to APs, or to lower modulations client devices withrelatively lower SNR that are farther away from the APs. However, OFDMis not capable of supporting both client device types at the same time.OFDMA technology in the 802.11ax standard does—it can cater to bothclient device types (high modulation/close and low modulation/far)within one transmit burst. Thus, OFDMA inherently promises lower overalllatency in a WiFi cell by making “efficient” use of the available RFspectrum. Hence, the association “High Efficiency,” i.e., 802.11ax HighEfficiency WLAN allows for scheduling multi-user DL and ULtransmissions.

However, although the 802.11ax standard allows for the presence ofvarying modulations and transmit powers within one transmit burst, PAlinearity is challenged, and thus, a PA's ability to preserve its signalquality over distances, may be sacrificed. Linearity in the RF senserefers to the PA's objective of increasing the power level of an inputsignal without otherwise altering the content of that signal. In otherwords, a linear PA is an electronic circuit whose output is proportionalto its input, but is nevertheless able to deliver more power into aload.

Common WiFi deployments, at a high level, can be grouped into twocategories. A first type of WiFI deployment can be referred to as adense deployment which caters to high throughput client devices. Asecond type of WiFI deployment can be referred to as a relatively sparsedeployment, which is typically geared towards covering long ranges oflow throughout client devices. Ideally, the fastest throughout over longdistances would be desirable, but the physics of RF front end design isincapable of addressing both types of deployments/client devices at thesame time. Although more advanced PAs may be able to boost the range ofhigher modulations client devices, the throughput versus range tradeoffwill always exist for any given PA. In addition to cost and powerconsumption, using high linearity PAs forces a design to usesophisticated thermal solutions because of the heat generated due totheir higher power consumption, which also results in increased cost.Hence, using very high linearity and expensive PAs to overcome signalquality issues arising from varying powers in OFDMA transmissions can beconsidered to be an inefficient and non-optimized engineering design.

Some 802.11ax WiFi radio chip vendors are addressing the PA linearityissue associated with OFDMA transmissions by grouping client deviceswith similar rates (and hence TX power) within one PA burst. However,such a rigid grouping algorithm can be restrictive, and can ultimatelydiminish the improved latency promises of the 802.11ax standard.Therefore, as alluded to above, and as described in detail below,optimization techniques are disclosed to enhance the existing OFDMAdownlink scheduler algorithm/mechanism to improve latency withoutrunning afoul of PA linearity. This can be accomplished by firstattempting selective RF boosting/de-boosting of RUs to accommodate bothhigh SNR/close proximity client devices and lower SNR client devicesthat are further from an AP. The manner in which theboosting/de-boosting may follow an algorithm that allows summation ofall transmit powers across all RUs in a transmit burst to remain somethreshold amount of power (in dB) backed off from the saturated outputpower of the PA such that after the back-off, the total power is lessthan the most complex modulation-limited power for that transmit burst.

If such selective RF boosting/de-boosting is not supported, an enhancedOFDMA grouping mechanism can be applied to skip higher transmission/MCSrates. In particular, based on an OFDMA candidate list (where clientdevices have been grouped according to a conventional rigid groupingalgorithm), the grouping is enhanced. That is, the rigid grouping ofclient devices can be enhanced or refined to create larger groups thatencompass client devices across more MCS rates, while those clientdevices can still be accommodated in a single transmit burst using PApowers that are sufficiently proximate to each other such that, again,PA linearity can be maintained.

FIG. 1 illustrates one embodiment of a network configuration 100 thatmay be implemented for a multi-user organization, such as a business,educational institution, governmental entity, or any other organizationhaving multiple users and possibly multiple physical or geographicalsites. The network configuration 100 may include a main office 102 incommunication with a network 120. The network configuration 100 may alsoinclude one or more remote sites 132, 142, that are in communicationwith the network 120.

The main office 102 may include a primary network, which can be referredto as a corporate network or a home network. The main office 102 networkmay be a private network. A private network can refer to a network thatmay include security and access controls, such that only certain usersare authorized to access the private network. Authorized users mayinclude, for example, employees of a company based in the main office102.

In the illustrated example, the main office 102 includes a controller104 in communication with the network 120. The controller 104 mayprovide communication with the network 120 for the main office 102,though it may not be the only point of communication with the network120 for the main office 102. A single controller 104 is illustrated,though the main office may include multiple controllers and/or multiplecommunication points with network 120. In some embodiments, thecontroller 104 communicates with the network 120 through a router (notillustrated). In other embodiments, the controller 104 provides routerfunctionality to the devices in the main office 102.

A controller 104 may be operable to configure and manage networkdevices, such as at the main office 102, and may also manage networkdevices at the remote sites 132, 134. The controller 104 may be operableto configure and/or manage switches, routers, access points, and/orclient devices connected to a network. The controller 104 may itself be,or provide the functionality of, an access point.

The controller 104 may be in communication with one or more switches 108and/or wireless APs 106 a-c. Switches 108 and wireless APs 106 a-cprovide network connectivity to various client devices 110 a-j. Using aconnection to a switch 108 or AP 106 a-c, a client device 110 a-j isable to access network resources, including other devices on the (mainoffice 102) network and the network 120.

Examples of client devices include, but are not limited to: desktopcomputers, laptop computers, servers, web servers, authenticationservers, authentication-authorization-accounting (AAA) servers, DomainName System (DNS) servers, Dynamic Host Configuration Protocol (DHCP)servers, Internet Protocol (IP) servers, Virtual Private Network (VPN)servers, network policy servers, mainframes, tablet computers, netbookcomputers, televisions and similar monitors, content receivers, set-topboxes, personal digital assistants (PDAs), mobile phones, smart phones,smart terminals, dumb terminals, virtual terminals, video game consoles,and the like.

Within the main office 102, a switch 108 is included as one example of apoint of access to the network established in main office 102 for wiredclient devices 110 i-j. Client devices 110 i-j may connect to the switch108 and through the switch 108, may be able to access other deviceswithin the network configuration 100. The client devices 110 i-j mayalso be able to access the network 120, through the switch 108. Theclient devices 110 i-j may communicate with the switch 108 over a wired112 connection. In the illustrated example, the switch 108 communicateswith the controller 104 over a wired 112 connection, though thisconnection may also be wireless.

Wireless APs 106 a-c are included as another example of a point ofaccess to the network established in main office 102 for client devices110 a-h. Each of APs 106 a-c may be a combination of hardware, software,and/or firmware that is configured to provide wireless networkconnectivity to wireless client devices 110 a-h. In the illustratedexample, APs 106 a-c can be managed and configured by the controller104. APs 106 a-c communicate with the controller 104 and the networkover either wired 112 or wireless 114 connections.

The network configuration 100 may include one or more remote sites 132.A remote site 132 may be located in a different physical or geographicallocation from the main office 102. In some cases, the remote site 132may be in the same geographical location, or possibly the same building,as the main office 102, but lacks a direct connection to the networklocated within the main office 102. Instead, remote site 132 may utilizea connection over a different network, e.g., network 120. A remote site132 such as the one illustrated in FIG. 1 may be, for example, asatellite office. The remote site 132 may include a gateway device 134for communicating with the network 120. A gateway device 134 may be arouter, a digital-to-analog modem, a cable modem, a Digital SubscriberLine (DSL) modem, or some other network device configured to communicateto the network 120. The remote site 132 may also include a switch 138and/or AP 136 in communication with the gateway device 134 over eitherwired or wireless connections. The switch 138 and AP 136 provideconnectivity to the network for various client devices 140 a-d.

In various embodiments, the remote site 132 is in direct communicationwith main office 102, such that client devices 140 a-d at the remotesite 132 access the network resources at the main office 102 as if theseclients devices 140 a-d were located at the main office 102. In suchembodiments, the remote site 132 is managed by the controller 104 at themain office 102, and the controller 104 provides the necessaryconnectivity, security, and accessibility that enable the remote site132's communication with the main office 102. Once connected to the mainoffice 102, the remote site 132 may function as a part of a privatenetwork provided by the main office 102.

In various embodiments, the network configuration 100 may include one ormore smaller remote sites 142, comprising only a gateway device 144 forcommunicating with the network 120 and a wireless AP 146, by whichvarious client devices 150 a-b access the network 120. Such a remotesite 142 may represent, for example, an individual employee's home or atemporary remote office. The remote site 142 may also be incommunication with the main office 102, such that the client devices 150a-b at remote site 142 access network resources at the main office 102as if these client devices 150 a-b were located at the main office 102.The remote site 142 may be managed by the controller 104 at the mainoffice 102 to make this transparency possible. Once connected to themain office 102, the remote site 142 may function as a part of a privatenetwork provided by the main office 102.

The network 120 may be a public network, such as the Internet. A publicnetwork is a network that may be shared by any number of entities,including the illustrated network configuration 100. A public networkmay have unrestricted access, such that any user may connect to it. Thenetwork 120 may include third-party telecommunication lines, such asphone lines, broadcast coaxial cable, fiber optic cables, satellitecommunications, cellular communications, and the like. The network 120may include any number of intermediate network devices, such asswitches, routers, gateways, servers, and/or controllers, which are notdirectly part of the network configuration 100 but that facilitatecommunication between the various parts of the network configuration100, and between the network configuration 100 and othernetwork-connected entities. The network 120 may include various contentservers 160 a-b. Content servers 160 a-b may include various providersof multimedia downloadable and/or streaming content, including audio,video, graphical, and/or text content, or any combination thereof.Examples of content servers 160 a-b include, for example, web servers,streaming radio and video providers, and cable and satellite televisionproviders. The client devices 110 a j, 140 a-d, 150 a-b may request andaccess the multimedia content provided by the content servers 160 a-b.

FIG. 2 illustrates example radio circuitry 200 of an example AP, e.g.,one of the APs of network configuration 100 (FIG. 1). It should beunderstood that this is merely one, non-limiting example of an AP, andvarious embodiments are applicable to any/all 802.11ax-compliant APs.Radio circuitry 200 may include multiple components electrically coupledvia traces on a printed circuit board. In some examples, radio circuitry200 may be contained within a system on a chip (SOC). In some otherexamples, radio circuitry 200 is a combination of a SOC and otherdiscrete components. For example, certain radio circuitry 200 mayinclude an integrated circuit for each radio 202 and 204, an integratedcircuit for each front-end circuitry 208 a-c, and discrete componentsfor sub-band filter 216 and band filter 218. As another example, theradio circuitry of first radio 202 (including front-end circuitry 208 a,RF switches 212, sub-band filters 210, band filter 220 a, and antenna206 a) is contained within a SOC, and the radio circuitry of secondradio 204 is contained within another SOC. Although certain specificexamples of the physical layout of radio circuitry 200 have beendiscussed, this disclosure contemplates any physical arrangement ofcomponents, integrated circuits, and SOCs as appropriate.

In example radio circuitry 200, first radio 202 may be capable oftransceiving signals on channels within the 5 GHz frequency band. Incertain examples, first radio 202 is capable of transceiving signalswithin any appropriate frequency band, but the band filter 218 and thesub-band filter 216 restrict first radio 202 to transceiving signalswithin the 5 GHz frequency band. In certain configurations, first radio202 may be able to transceive signals within a sub-band of the 5 GHzfrequency band. Although first radio 202 is described in relation totransceiving signals on the 5 GHz frequency hand, it is contemplatedthat first radio 202 could transceive signals on any appropriatefrequency band, including the 2.4 GHz frequency band.

First radio 202 is coupled to front-end circuitry 208 a. In someexamples, front-end circuitry 208 a includes one or more PAs, e.g., PA208 a-1, one or more low noise amplifiers, one or more power detectors,and RF switches to bypass portions of front-end circuitry 208 a. Incertain examples, front-end circuitry 208 a may also be called afront-end module. In this disclosure, the term “RF switch” may refer toa device capable of routing an RF signal along one of two paths based onan input. This is in contrast to a “network switch,” which is anetworking component for routing packets to a destination device. Incertain examples, front-end circuitry 208 a includes power amplifiers.In certain other examples, front-end circuitry 208 a includes low noiseamplifiers. Coupled to front-end circuitry 208 a is sub-band filter 216.For the antenna circuitry coupled to first radio 202, sub-band filter216 may include a band-pass filter 210 a and a bypass 210 b controlledby single-pole double-throw (SPDT) RF switches 212. In some examples, RFswitches 212 toggle the antenna circuit between 5 GHz mode, and a 5 GHzsub-band mode. Sub-band filter 216 is coupled to band filter 218, whichincludes band-pass filter 220 a. Band-pass filter 220 a filters signalsso that signals within the 5 GHz frequency band pass through band filter218. Band filter 218 is coupled to antenna 206 a.

In one example configuration, a signal is received at antenna 206 a. Thesignal may include noise, which may include signals from undesiredsources, harmonic signals from desired sources, and distortions of thesignal as transmitted. By passing the signal through band filter 218,band-pass filter 220 a filters out all portions of the signal that arenot within the desired frequency band. From band filter 218, the signalproceeds to sub-band filter 216. RF switch 212 b routes the signal toband-pass filter 210 a, which, similar to band-pass filter 220 a,filters out all undesired portions of the signal. Band-pass filter 210 afilters all portions of the signal that are not within a desiredsub-band of the desired frequency band. The signal then proceeds throughRF switch 212 a and out of sub-band filter 216 to front-end circuitry208 a. Front-end circuitry 208 a receives the signal and amplifies it.In some examples, front-end circuitry 108 a further reduces noise in thesignal while amplifying the desired portions of the signal. Fromfront-end circuitry 208 a, the signal passes to first radio 202, whichprocesses the signal for use in network communications. In anotherexample configuration, a signal is received at antenna 206 a. From bandfilter 218, the signal proceeds to sub-band filter 216. RF switch 212 broutes the signal to bypass 210 b, avoiding band-pass filter 210 a.Since no sub-band filtering occurs, the signal is still filtered to thedesired frequency band. The signal then proceeds through RF switch 212 aand out of sub-band filter 216 to front-end circuitry 208 a. Front-endcircuitry 208 a receives the signal and amplifies it. In some examples,front-end circuitry 208 a further reduces noise in the signal whileamplifying the desired portions of the signal. From front-end circuitry208 a, the signal passes to first radio 202, which processes the signalfor use in network communications.

In example radio circuitry 200, second radio 204 is capable oftransceiving signals on channels within the 5 GHz frequency band and onchannels within the 2.4 GHz frequency band. In certain examples, secondradio 204 is capable of transceiving signals within any appropriatefrequency band, but the band filter 218 and the sub-band filter 216restrict second radio 204 to transceiving signals within the 5 GHz and2.4 GHz frequency band, but second radio 204 could transceive signals onany appropriate frequency band.

Second radio 204 is coupled to front-end circuitry 208 b and 208 c. Insome examples, front-end circuitry 208 b and 208 c each include at leastone PA, e.g., PA 208 b-1 and PA 208 b-2, at least one low noiseamplifier, at least one power detector, and multiple RF switches tobypass portions of front-end circuitry 208 b and 208 c. In certainexamples, front-end circuitry 208 b and 208 c may also be called afront-end module. Coupled to front-end circuitry 208 b and 208 c,respectively, is sub-band filter 216. For the antenna circuitry coupledto second radio 204, sub-band filter 216 may include a band-pass filter214 a. Front-end circuitry 208 b is coupled to band-pass filter 214 aand front-end circuitry 208 c is coupled to band-pass filter 214 b. Insome examples, second radio 204 is configured in one of: a 5 GHzsub-band mode, and a 2.4 GHz mode. Sub-band filter 216 is coupled toband filter 218, which includes filter 220 b. Filter 220 b filterssignals so that signals within the desired frequency band pass throughband filter 218. Band filter 218 is coupled to antenna 106 b. Signalsreceived at antenna 206 b may processed similar to the manner in whichsignals received at antenna 206 a are processed via filter 220 b, one ofbandpass filters 214 a/214 b, one of front-end circuitry 208 b/208 c,and on to second radio 204, which processes the signal for use innetwork communications.

Conventionally-implemented rigid grouping of clients according to MCStypically results in the selection of a minimum TX power for differentmodulations within an OFDMA transmit burst. However, this rigid groupingscheme has a shortcoming in that it does not allow for the presenceof/communications with a “distant” client device (within a singletransmit burst), which is forced to use lower rates such as MCS0 due toSNR degradation arising from higher path loss. Depending upon thelatency needs of higher modulation client devices, this can lead tosignificantly worse latency for the client device using MCS0. It shouldbe understood that that MCS are used to determine the data rate of awireless connection. Although certain examples/scenarios describedherein refer to a particular set of MCS, i.e., MCS0-MCS11, more MCS maybe defined by the 802.11xx standard. Various embodiments can beadaptable across other MCS/MCS sets.

In accordance with one embodiment, boosting and de-boosting of RUs suchthat the average input power to the PA in time domain is 6-8 dB belowPsat (saturated output power of the amplifier) of the PA. The examplesdescribed herein may refer to certain MCS, transmit powers, powerthresholds/boundaries, etc. It should be understood that transmissionpowers corresponding to a particular MCS refers to a characteristics ofa given PA, and so such transmit powers, power thresholds, etc. maydiffer and are configurable depending on the system, PAs utilized inAPs, and so on. Achieving this 6-8 dB back-off can ensure that the PA islinear enough for MCS9-MCS11 on all RUs, but also allows the use of afew RUs at higher power to cater to the SNR of distant MCS0 or low-MCSclient devices.

FIG. 3 illustrates two examples of such boosting/de-boosting using26-tone RUs in a 20 MHz channel. As illustrated in FIG. 3, a firstboosting/de-boosting example 300 involves nine client devices with whichan AP may communicate using nine approximately 2 MHz RUs. In this firstboosting/de-boosting example 300, it can be appreciated that the clientdevices associated with RU1-RU8 are proximate/near to the AP and may behigh throughput client devices. The power used to communicate with suchclient devices may be approximately 3.00 dBm, while the power used tocommunicate with the client device (that may be further away from theAP) using RU9 may be approximately 10 dBm. The total power across allRUs is 14.14 dBm (understanding that dBm is a logarithmic power unit,i.e., the sum of all the powers is typically calculated by firstconverting the logarithmic values into linear values, adding the linearvalues, and converting the linear sum back into a logarithmic value).

A second boosting/de-boosting example 302 illustrated in FIG. 3 involvesseven client devices with which an AP communicates using RU1-RU7,respectively, at a power of 3.5 dBm. These client devices are close tothe AP and are high throughput client devices. In contrast, clientdevices with which the AP communicates using RU8 and RU9 are clientdevices that can be further away (relatively) from the AP and are lowerthroughput client devices. In this example 302, the total power acrossall RUs is 14.99 dBm. It should be appreciated that in both examples,distantly-located client devices can be serviced at approximately 6 dBhigher power that can provide a significant advantage in the context ofsparse deployments.

In conventional systems/using conventional mechanisms, a single PAtransmission could not accommodate both types of clients describedabove. To accommodate a client that is further away from an AP(requiring higher power), PA linearity is limited, i.e., boosting powerof an RU results in more difficulty keeping input signals proportionalto output signals of the PA. Thus, instead of equally dividing poweramongst all RUs (as may be done conventionally), the power of RUs usedto access/communicate with client devices that are further away from theAP can be boosted, while the power of RUs used to access/communicatewith client devices that are closer to the AP can be reduced, i.e.,de-boosted. When using typical, median PAs, a total average poweracross, in these examples, a 20 MHz channel of 14.14 dBm or 14.99 dBm isapproximately 6-8 dBm less than the Psat of such PAs. Operation of a PAat approximately 6-8 dBm below its Psat, results in linear operation ofthe PA, which in turn results in maintaining the quality of the signaloutput from the PA. In this way, both types of client devices areaccommodated, and this can be accomplished without sacrificing PAlinearity.

In accordance with one embodiment, a boosting/de-boosting algorithm isused to determine the requisite power distribution across the multipleRUs for a single transmit burst. The algorithm described below is oneexample of effectuating boosting/de-boosting, but other algorithms maybe used/developed to accomplish the desired power distribution in othercontemplated embodiments.

${{\sum\limits_{i = 1}^{m}P_{{LowMSC},i}} + {\sum\limits_{i = {m + 1}}^{n}P_{{HighMSC},i}}} \leq {P_{sat} - x}$

It should be understood that: m can refer to the total number of low MCSRUs, n can refer to the total number of RUs in an OFDMA transmit burst;P_(low MCS, i) can refer to the power of the i^(th) low MCS RU, whileP_(high MCS, i) can refer to the power of the i^(th) high MCS RU. Ingeneral, the boosting/de-boosting of RU powers should be some desiredamount less than the P_(sat) of the PA to maintain linearity, i.e., thesummation of all RU powers should be “x” dBs backed-off/less than theP_(sat) such that P_(sat)−x dBm is equal to or less than the mostcomplex modulation limited power in a particular transmit burst. Inother words:

${\sum\limits_{i = {m + 1}}^{n}P_{{RU},i}} \leq {P_{sat} - x}$

∀(P_(sat)−x)≤1024QAM or 4096QAM limited power for a given PA

That is, the total power of low MCS RUs plus the total power of high MCSRUs should be the desired 6-8 dB less than the PA Psat. The practicaleffect is that low MCS RUs are separated from high MCS RUs byapproximately 6-8 dB, where the function is bound to be no more than 12dB in difference (although, as alluded to above, this is configurable).Limiting the difference can be accomplished with the following function.|P _(Low MSC,i) −P _(High MSC,i)≤12 dB|

Referring back to FIG. 3, it can be appreciated that RU9 is separatedfrom each of RUs1-8 by about 7 dB per the boosting/de-boosting example300, and RU8 and RU9 are separated from each of RUs1-7 by about 5.5 dBper the boosting/de-boosting example 302. It should be noted that thepower spectral density (PSD), i.e., power per MHz, per RU in theseexamples 300/302, are comparable to 802.11ac and 802.11n deployments,especially campus deployments. FIG. 4 illustrates an example EffectiveIsotropic Radiated Power (EIRP) distribution histogram representative ofreal-world statistics obtained from a campus deployment. The x-axis(cl_actual_eirp_10× Ascending) refers to measured/detected EIRP from APsof the campus deployment (multiplied by a power of 10). It should beunderstood that the multiplication factor of 10 is typically reflectedin such measurements. The y-axis (Count) refers to the number oftransmit power events measured every minute over several days associatedwith approximately 200,000 APs making up the campus deployment. Thus,the EIRP distribution histogram represents power radiated by the APs ofthe campus deployment.

It can be appreciated that power distribution resides mostly within the9 dBm (90/10) to 18 dBm (180/10) range, the highest appreciable EIRPvalue being 21 dBm (210/10), which corresponds with the power used inapproximately 2,500,000 transmit power events at the APs. As anotherexample, almost 15,000,000 transmit power events occurred at a power of18 dBm, while almost 18,000,000 transmit power events occurred at apower of 9 dBm. Taking the highest appreciable power, e.g., 21 dBm(210/10), and by subtracting approximately 3 dB to account for antennagain and approximately 6 dB MIMO gain to account for multiple radiochains, e.g., in this case, a 4×4 radio, the maximum conducted power perradio chain is approximately 12 dBm. This translates into a PSD level of−1 dBm/MHz or 2 dBm per 2 MHz RU for a 20 MHz channel bandwidth that isactually lower than the 3-3.5 dBm per 2 MHz RU used for the highmodulations in examples 300/302. This translation from −1 dBm/MHz to 2dBm/2 MHz is to normalize the PSD/make it comparable to the 2 MHz RUs(of a 20 MHz channel).

That is, and referring back to FIG. 3, in the case of the firstboosting/de-boosting example 300, it can be appreciated that despiteboosting/de-boosting power for RUs to accommodate client devicesgeographically near to an AP (RU1-RU8), as well as client devices thatare geographically far/farther from that AP (RU9), the amount ofde-boosting applied to nearby client devices (at 3.00 dBm) is in line(from a practical standpoint) with the measured power in a typicaldeployment, such as a campus deployment. The same holds true for example302, where 3.5 dBm PSD per RU is again in line with that of a typicaldeployment, despite now also being able to accommodate for clientdevices farther away (RU8-RU9) from an AP simultaneously with clientdevices (RU1-RU7) closer to the AP.

It should be understood that boosting/de-boosting in the 802.11axstandard is used from the MCS perspective, i.e., to balance modulationcoding. This is in contrast to the manner/reason for its use in variousembodiments disclosed herein, where boosting/de-boosting can beperformed from the RF perspective. That is, if one client device(further away from an AP) is using MCS6, and another client device(closer to the AP) is using MCS 11, the power level for the lower MCS6client can be boosted by approximately 3-6 dB, and the power level ofthe higher MCS11 client (and likely other high MCS clients) can beproportionately de-boosted such that the total power remainsapproximately 6 to 8 dB below Psat. Practically speaking, however, APvendors' scheduling algorithm(s) (which take advantage of DL MU-MIMO)already group like-MCS client devices. For example, a conventionalscheduling algorithm would typically not contemplate a grouping of MCS0client devices with MCS11 client devices, and so any advantageassociated with boosting RU power would be negated. However, in the RFcontext, and as noted above, use of boosting/de-boosting in the mannerdisclosed herein can be an effective way to manage/maintain PAlinearity.

If RU power boosting/de-boosting, however, is unsupported by the radiochip (FIG. 2), a mechanism for OFDMA grouping may be applied. It shouldbe noted that conventional OFDMA grouping mechanisms exist, but arepremised on a rigid grouping of MCSs. Conventional, rigid grouping canresult in smaller groups that use the lowest power associated with anMCS within a given group. For example, FIG. 5 presents an example ofconventional OFDMA grouping, where twelve MCS rates (MCS0-MSC11) aredivided into four groups of three MCSs each. Based on PA linearitycharacteristics, a maximum RF power at which each transmission rate/MCScan transmit is reflected as follows. For MCS0-2, the maximum power is17 dBm (commensurate with the lowest maximum power associated with anyof MCS0-2). Thus, for all client devices using MCS0-2, the power usedwill be 17 dBm. For MCS3-5, the group maximum power is 15.5 dBm(commensurate with the max power possible while retaining PA linearityassociated with MCS5). Thus, for all client devices using MCS3-5, thepower used will be 15.5 dBm. Similarly, the maximum group power ofMCS6-8 is 13 dBm, and the maximum group power of MCS9-11 is 10 dBm.Thus, even though PA linearity-limited powers allow for, e.g., 15 dBm,14 dBm, and 13 dBm (in the case of MCS6-8) the power is limited to 13dBm. Of course, this topology may have a slight SNR impact on MCS6 andcould impact the range of MCS6 client devices in sparse deployments.

Another shortcoming of conventional, rigid OFDMA grouping can be seen atthe boundary of two high modulation groups. Consider an OFDMA groupincluding MCS6, MCS7, MCS8 and MCS9 client devices. When transmitting aburst containing MCS9, the algorithm will force MCS6, MCS7 and MCS8(slightly lower SNR clients) out of the transmission. In most practicaldeployments, because of obstructions, there are more MCS6, MCS7 and MCS8clients than MCS9, MCS10 and MCS11 clients. Hence, rigid grouping couldlead to serious latency issues for MCS6, MCS7 and MCS8 client devices.

In accordance with various embodiments, a new/additional groupingalgorithm can be used, following this example, where MCS10 and MCS11(1024-QAM modulation) is not used. Instead, MCS9 may be used for thoseMCS10 and MCS11 client devices. In this way, even without the ability toboost/de-boost RU power, various embodiments are nevertheless, able toaccommodate larger numbers of high modulation client devices, and stillhave reduced latency (at a slight instantaneous throughput penalty fortrue MCS10/MCS11 client devices). It should be understood that “true” inthis context, can refer to client devices once using/supposed to use, inthis example, MCS10/MCS11 prior to grouping in accordance with variousembodiments. That is, MCS10/MCS11 client devices have sufficiently goodSNR to handle MCS10/MCS11 modulations, but are restricted to MCS9 inaccordance with one embodiment.

FIGS. 6A and 6B illustrate a flow chart of operations that may beperformed to achieve enhanced OFDMA grouping in accordance with oneembodiment. It should be understood that FIG. 6A represents operationsthat may already be performed in accordance with conventional APscheduling, but lead to application of enhanced grouping as disclosedherein. The grouping algorithm starts at operation 600, and proceeds tooperation 602, which involves activating a traffic identifier (TID)candidate list, i.e., those users or candidates with active TID queuesare considered. It should be understood that WLAN packets can be streamsof video, voice, data, each of which may have a different priority to beserved by an AP. The TID can be used to classify a packet such that uponreceipt of a frame, a certain priority can be assigned based on the TIDassociated with the frame.

At operation 604, stage 1 scheduling may be performed by, at operation606, querying the rate control module 608 which can choose between fixedrate assignment and rate adaption based, e.g., on current channelconditions. That rate can be returned, based on thereon, at operation610, a MU-MIMO candidate list can be derived, and at operation 612,based on the candidate list, candidates/client devices can be grouped.For SU-MIMO, at operation 614, another candidate list can be determined,after which, at operation 616 SU-MIMO transmissions from thosecandidates/client devices may commence. That is, the scheduler(scheduling mechanism effectuated through instructions stored in amemory of an AP and executed by a processor of the AP) may select aparticular transmit mode based on various considerations, including,e.g., the number of client devices/candidates at issue, their respectivecapabilities, respective queue depths (indicating the amount of trafficto be sent from each client device), and rate assigned to each clientdevice by the rate control module 608. At operation 618, an OFDMAcandidate list is considered, where the MCS value is assigned to eachuser/client device.

As illustrated in FIG. 6B, at stage 1, and based on standard PhysicalLayer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) duration,the rate and the amount of traffic to be sent for the client device, anRU allocator module or component of an AP groups the client devices, andassigns the RUs to the client devices. It should be understood that anAP may have a processor and memory containing instructions that whenexecuted cause the processor to perform RU allocation, as well as OFDMAgrouping as disclosed herein.

At operation 622, the method progresses by iterating through theassigned MCS of each of the candidates/client devices in the OFDMAcandidate list.

At operation 624, a check may be performed to determine if the minimumMCS in a given group is greater than 10. If so, a PPDU can betransmitted with the default power assigned to each client device basedon the rate, as PA linearity can be met. That is, and in this example,if the minimum MCS in a group is MCS10, only MCS10/MCS11 clients devicesneed to be addressed in one transmit burst. Thus, the PA need not dealwith low and high SNR clients at the same time, and linearity issues areavoided. If the minimum MCS of the given group is less than 10, a checkmay be performed at operation 626 to determine If the minimum MCS isless than 7. If so, at operation 628, the MCS of MCS 10 and MCS 11 maybe capped at/dropped to MCS 9, and MCS 5 and MCS 6 are dropped/capped toMCS 4. Additionally, two buckets or groups covering MCS ranges MCS0-MCS4and MCS7-MCS9 can be created.

The process my proceed to operation 634, where a second stage, stage 2,of RU allocation and grouping can be performed with respect to the twosets of client devices. It should be noted that operation 634 isperformed to account for the fact that RU requirements will changebecause of a change in transmission rate. In stage 2, therefore, the RUsizes in a given group are re-calculated, and the PPDU can betransmitted.

If the minimum MCS is greater than or equal to MCS7 (operation 626), atoperation 630, a check is performed to determine if the maximum MCS inthe group is less than 10. This can refer to the case of MCS7, MCS8, andMCS9 belonging to a group, and transmission of data can occur using thedefault transmit power values assigned (assigned transmit power valuesbased on conventional rigid grouping). If the minimum MCS is indeedgreater than or equal to MCS7, and the maximum MCS is greater than MCS9,i.e., MCS7, 8, 9, 10, and 11 are grouped together, the MCS of MCS10 andMCS11 are dropped/capped to MCS9 at operation 632. It should beunderstood that operation 630, by virtue of checking whether the maximumMCS is less than 10, accounts for checking if a maximum MCS is greaterthan 9. Thereafter, and again, at operation 634, stage 2 RU allocationand grouping can be performed.

It should be noted that the checks and caps according to MCS describedabove with respect to, e.g., FIG. 6B and otherwise described herein, aremerely examples provided in the context of a given group of MCS (in thisexample MCS0-MCS11). As noted above, other MCSs exists/may be used, andvarious embodiments can be adapted accordingly. That is, grouping inaccordance with various embodiments can be flexible, and in general, ispremised on dropping the highest MCS rates to one or two lower MCSrates. This allows for more client devices to be covered/serviced withless MCS rates in a group, thus allowing the PA to remain linear.

FIG. 7 is a block diagram of an example computing component or device200 for optimizing scheduling of downlink OFDMA transmissions inaccordance with one embodiment. Computing component 700 may be, forexample, a server computer, a controller, or any other similar computingcomponent capable of processing data. In the example implementation ofFIG. 7, the computing component 700 includes a hardware processor, 702,and machine-readable storage medium, 704. In some embodiments, computingcomponent 700 may be an embodiment of an AP or AP controller, e.g., AP106 b or AP controller 104, respectively, of FIG. 1.

Hardware processor 702 may be one or more central processing units(CPUs), semiconductor-based microprocessors, and/or other hardwaredevices suitable for retrieval and execution of instructions stored inmachine-readable storage medium, 204. Hardware processor 702 may fetch,decode, and execute instructions, such as instructions 706-710, tocontrol processes or operations for grouping client devices based ontraffic compatibility. As an alternative or in addition to retrievingand executing instructions, hardware processor 702 may include one ormore electronic circuits that include electronic components forperforming the functionality of one or more instructions, such as afield programmable gate array (FPGA) or application specific integratedcircuit (ASIC).

A machine-readable storage medium, such as machine-readable storagemedium 704, may be any electronic, magnetic, optical, or other physicalstorage device that contains or stores executable instructions. Thus,machine-readable storage medium 704 may be, for example, Random AccessMemory (RAM), non-volatile RAM (NVRAM), an Electrically ErasableProgrammable Read-Only Memory (EEPROM), a storage device, an opticaldisc, and the like. In some embodiments, machine-readable storage medium702 may be a non-transitory storage medium, where the term“non-transitory” does not encompass transitory propagating signals. Asdescribed in detail below, machine-readable storage medium 702 may beencoded with executable instructions, for example, instructions 706-710for optimizing OFDMA downlink transmission scheduling.

Hardware processor 702 may execute instruction 706 to determine whethera WLAN device, such as an AP, supports RU boosting/de-boosting. Itshould be understood that based on the radio chipset, this capability isknown.

Hardware processor 702 may execute instruction 708 to, in response to adetermination that RU boosting/de-boosting is supported, at least one ofboost and de-boost power applied to each of a plurality of RUs belongingto an OFDMA channel and transmitted in a single transmit burst. As notedabove, each of the RUs assigned to carry data transmitted by a differentclient device associated to the WLAN device is boosted/de-boosted suchthat an average input power to a PA of the WLAN device remains below asaturated output power of the PA. In this way, both highthroughput/nearby client devices as well as low throughput/distantclient devices can be supported without adversely impacting thelinearity of the PA(s).

Hardware processor 702 may execute instruction 710 to, in response todetermining boosting/de-boosting of RUs is unsupported, group aplurality of MCS transmission rates, and transmit the data in accordancewith a lower maximum power associated with one of the plurality of MCStransmission rates in each of the groups. Unlike conventional rigidgrouping, the highest MCS rates in a group can be dropped to one or twolower MCS rates, such that more client devices can be covered/servicedwith less MCS rates, thus allowing the PA to remain linear.

It should be understood that OFDMA is a key feature in the 802.11ax(also referred to as WiFi 6) standard because it improves efficiency andreduces latency by grouping a large number of clients (up to 37 in a 80MHz channel bandwidth). Typical vendor algorithms group client devicesin an OFDMA transmission based on the MCS assigned to them which issub-optimal. Grouping based on MCS would result in smaller sized groupsand hence increase latency. In accordance with various embodiments, theoverall throughput may be impacted by a small percentage becausetransmission rates are reduced. However, overall, the disclosedmechanism is more efficient in terms of improving latency. In anenterprise deployment, the applications' performance suffer because oflatency requirements not being met and not because of throughput.Moreover, cost savings can be realized in the hardware platform by notrequiring the use of, e.g., expensive PAs for use in boosting the rangeof higher modulation client devices, that nevertheless are still victimto the throughput versus range tradeoff.

FIG. 8 depicts a block diagram of an example computer system 800 inwhich various of the embodiments described herein may be implemented.The computer system 800 includes a bus 802 or other communicationmechanism for communicating information, one or more hardware processors804 coupled with bus 802 for processing information. Hardwareprocessor(s) 804 may be, for example, one or more general purposemicroprocessors.

The computer system 800 also includes a main memory 806, such as arandom access memory (RAM), cache and/or other dynamic storage devices,coupled to bus 802 for storing information and instructions to beexecuted by processor 804. Main memory 806 also may be used for storingtemporary variables or other intermediate information during executionof instructions to be executed by processor 804. Such instructions, whenstored in storage media accessible to processor 804, render computersystem 800 into a special-purpose machine that is customized to performthe operations specified in the instructions.

The computer system 800 further includes a read only memory (ROM) 808 orother static storage device coupled to bus 802 for storing staticinformation and instructions for processor 804. A storage device 810,such as a magnetic disk, optical disk, or USB thumb drive (Flash drive),etc., is provided and coupled to bus 802 for storing information andinstructions.

In general, the word “component,” “system,” “database,” and the like, asused herein, can refer to logic embodied in hardware or firmware, or toa collection of software instructions, possibly having entry and exitpoints, written in a programming language, such as, for example, Java, Cor C++. A software component may be compiled and linked into anexecutable program, installed in a dynamic link library, or may bewritten in an interpreted programming language such as, for example,BASIC, Perl, or Python. It will be appreciated that software componentsmay be callable from other components or from themselves, and/or may beinvoked in response to detected events or interrupts. Softwarecomponents configured for execution on computing devices may be providedon a computer readable medium, such as a compact disc, digital videodisc, flash drive, magnetic disc, or any other tangible medium, or as adigital download (and may be originally stored in a compressed orinstallable format that requires installation, decompression ordecryption prior to execution). Such software code may be stored,partially or fully, on a memory device of the executing computingdevice, for execution by the computing device. Software instructions maybe embedded in firmware, such as an EPROM. It will be furtherappreciated that hardware components may be comprised of connected logicunits, such as gates and flip-flops, and/or may be comprised ofprogrammable units, such as programmable gate arrays or processors.

The computer system 800 may implement the techniques described hereinusing customized hard-wired logic, one or more ASICs or FPGAs, firmwareand/or program logic which in combination with the computer systemcauses or programs computer system 800 to be a special-purpose machine.According to one embodiment, the techniques herein are performed bycomputer system 800 in response to processor(s) 804 executing one ormore sequences of one or more instructions contained in main memory 806.Such instructions may be read into main memory 806 from another storagemedium, such as storage device 810. Execution of the sequences ofinstructions contained in main memory 806 causes processor(s) 804 toperform the process steps described herein. In alternative embodiments,hard-wired circuitry may be used in place of or in combination withsoftware instructions.

The term “non-transitory media,” and similar terms, as used hereinrefers to any media that store data and/or instructions that cause amachine to operate in a specific fashion. Such non-transitory media maycomprise non-volatile media and/or volatile media. Non-volatile mediaincludes, for example, optical or magnetic disks, such as storage device810. Volatile media includes dynamic memory, such as main memory 806.Common forms of non-transitory media include, for example, a floppydisk, a flexible disk, hard disk, solid state drive, magnetic tape, orany other magnetic data storage medium, a CD-ROM, any other optical datastorage medium, any physical medium with patterns of holes, a RAM, aPROM, and EPROM, a FLASH-EPROM, NVRAM, any other memory chip orcartridge, and networked versions of the same.

Non-transitory media is distinct from but may be used in conjunctionwith transmission media. Transmission media participates in transferringinformation between non-transitory media. For example, transmissionmedia includes coaxial cables, copper wire and fiber optics, includingthe wires that comprise bus 802. Transmission media can also take theform of acoustic or light waves, such as those generated duringradio-wave and infra-red data communications.

As used herein, the term “or” may be construed in either an inclusive orexclusive sense. Moreover, the description of resources, operations, orstructures in the singular shall not be read to exclude the plural.Conditional language, such as, among others, “can,” “could,” “might,” or“may,” unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or steps.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing, the term “including” shouldbe read as meaning “including, without limitation” or the like. The term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof. The terms “a” or“an” should be read as meaning “at least one,” “one or more” or thelike. The presence of broadening words and phrases such as “one ormore,” “at least,” “but not limited to” or other like phrases in someinstances shall not be read to mean that the narrower case is intendedor required in instances where such broadening phrases may be absent.

What is claimed is:
 1. A wireless local area network (WLAN) device, comprising: a processor; and a memory unit operatively connected to the processor and including computer code executable by the processor to: determine whether the WLAN device supports boosting and de-boosting of resource units (RUs); in response to a determination that the WLAN device supports boosting and de-boosting, at least one of one of boost and de-boost power applied to each of a plurality of RUs belonging to an orthogonal frequency division multiple access (OFDMA) channel and transmitted in a single transmit burst, each of the RUs assigned to carry data transmitted to a client device, such that an average input power to a power amplifier (PA) of the WLAN device remains below a saturated output power of the PA; and in response to a determination that the WLAN device does not support boosting and de-boosting, group a plurality of modulation coding scheme (MCS) transmission rates, and transmit the data in accordance with a lowest maximum power associated with one of the plurality of MCS transmission rates in each of the groups.
 2. The WLAN device of claim 1, wherein a difference between the average input power and the saturated output power comprises a backoff power equal to or lower than a power associated with a most complex MCS transmission rate of the plurality of MCS transmission rates in the single transmit burst.
 3. The WLAN device of claim 1, wherein the average input power remains approximately 6-8 dB below the saturated output power of the PA.
 4. The WLAN device of claim 1, wherein the PA remains linear across all MCS transmission rates supported by each of the plurality of RUs.
 5. The WLAN device of claim 1, wherein the power applied to a first subset of the plurality of RUs is boosted, the first subset of RUs being used to at least one of access and communicate with a first subset of corresponding client devices.
 6. The WLAN device of claim 4, wherein the power applied to a second subset of the plurality of RUs is de-boosted, the second subset of RUs being used to at least one of access and communicate with a second subset of corresponding client devices.
 7. The WLAN device of claim 5, wherein each of the second subset of corresponding client devices are geographically nearer to the WLAN device than each of the first subset of corresponding client devices.
 8. The WLAN device of claim 1, wherein the memory unit comprises computer code that when executed, further causes the processor to select a transmit mode.
 9. The WLAN device of claim 8, wherein the memory unit comprises computer code that when executed, further causes the processor to, upon selection of an OFDMA transmit mode, receive an OFDMA candidate list, the OFDMA candidate list including an initial assignment of MCS transmission rates to each of the different client devices.
 10. The WLAN device of claim 9, wherein the memory unit comprises computer code that when executed, further causes the processor to group subsets of the different client devices based on Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) duration, rate at which traffic is to be sent for each of the different client devices, and an amount of traffic to be sent for each of the different client devices.
 11. The WLAN device of claim 9, wherein the memory unit comprises computer code that when executed, further causes the processor to assign each of the RUs to each of the different client devices.
 12. An access point, comprising: a processor; and a memory unit operatively connected to the processor and including computer code executable by the processor to: analyze an initial grouping of modulation coding scheme (MCS) transmission rates assigned to each of a plurality of client devices associated to the access point; adjust the initial grouping the MCS transmission rates in accordance with maximum radio frequency (RF) power levels at which traffic to the plurality of client devices are to be transmitted associated with each of the MCS transmission rates such that the traffic is transmitted with a lowest maximum power associated with one of the plurality of MCS transmission rates in each of the adjusted groups of MCS transmission rates.
 13. The access point of claim 12, wherein the memory unit comprises computer code that when executed, further causes the processor to boost power applied to each of a first subset of a plurality of resource units (RUs) assigned to carry data for a corresponding first subset of the plurality of client devices.
 14. The access point of claim 13, wherein the memory unit comprises computer code that when executed, further causes the processor to de-boost power applied to each of a second subset of the plurality of RUs assigned to carry data for a corresponding second subset of the plurality of client devices.
 15. The access point of claim 14, wherein each of the second subset of the plurality of client devices is geographically nearer to the WLAN device than each of the first subset of the plurality of client devices.
 16. An access point, comprising: a processor; and a memory unit operatively connected to the processor and including computer code executable by the processor to, if boosting and de-boosting of resource units (RUs) is enabled: boost power applied to each of a first subset of the RUs assigned to carry data for a corresponding first subset of client devices associated to the access point; and de-boost power applied to each of a second subset of the RUs assigned to carry data for a corresponding second subset of the plurality of client devices, such that an average input power to a power amplifier (PA) of the access point remains below a saturated output power of the PA.
 17. The access point of claim 16, wherein a difference between the average input power and the saturated output power comprises a backoff power equal to or lower than a power associated with a most complex MCS transmission rate of the plurality of MCS transmission rates in the single transmit burst.
 18. The access point of claim 16, wherein the average input power remains approximately 6-8 dB below the saturated output power of the PA.
 19. The access point of claim 16, wherein the PA remains linear across all MCS transmission rates supported by each of the RUs.
 20. The access point of claim 16, wherein the memory unit comprises computer code that when executed, further causes the processor to, in response to a determination that boosting and de-boosting of RUs is not enabled, group a plurality of modulation coding scheme (MCS) transmission rates, and transmit the data in accordance with a lowest maximum power associated with one of the plurality of MCS transmission rates in each of the groups. 